The present invention relates to back-end-of-line (BEOL) semiconductor processing, and more specifically, to preclean and nitridation prior to metallization of copper (Cu) vias.
Currently, preclean is accomplished by placing a semiconductor wafer into a preclean chamber and producing a hydrogen (H) plasma in the preclean chamber. Alternatively, preclean could be accomplished on a singulated die, and throughout the remainder of this disclosure “wafer” is meant to include both bulk wafer and singulated die or plurality of dies. A mechanical ion filter, such as a porous ceramic or quartz screen, is provided in the preclean chamber between the plasma and the die to prevent H+ ions of the plasma contacting and damaging the dielectric structure of the die. Conventionally, the mechanical filter is vacuum sealed to inner walls of the preclean chamber. After preclean, the semiconductor wafer is moved to a nitridation chamber, in which a nitrogen (N) plasma is produced to interact with the dielectric surface. In order to let the nitrogen ions contact the dielectric and accomplish nitridation, the nitridation chamber does not have any ion filter.